4a^2-21+5=0

Solution for 4a^2-21+5=0 equation:

Simplifying
4a2 + -21 + 5 = 0

Reorder the terms:
-21 + 5 + 4a2 = 0

Combine like terms: -21 + 5 = -16
-16 + 4a2 = 0

Solving
-16 + 4a2 = 0

Solving for variable 'a'.

Move all terms containing a to the left, all other terms to the right.

Add '16' to each side of the equation.
-16 + 16 + 4a2 = 0 + 16

Combine like terms: -16 + 16 = 0
0 + 4a2 = 0 + 16
4a2 = 0 + 16

Combine like terms: 0 + 16 = 16
4a2 = 16

Divide each side by '4'.
a2 = 4

Simplifying
a2 = 4

Take the square root of each side:
a = {-2, 2}